Drivers control the speed of a vehicle such as a truck or automobile by modulating an accelerator pedal. Mechanical linkages and valves control the flow of air and fuel to the engine based on the position of the accelerator pedal. When the driver depresses the accelerator pedal, the flow of air and fuel to the cylinders varies to increase engine speed.
Electronic throttle control (ETC) systems replace the mechanical accelerator pedal assemblies that are currently used in vehicles. ETC systems include one or more accelerator pedal position sensors, an ETC control algorithm and a controller such as the engine and/or powertrain controllers. ETC systems enhance powertrain management while reducing the manufacturing costs that are associated with mechanical pedal systems. ETC sensors eliminate the mechanical linkages and valves that are used to connect the accelerator pedal to the throttle body. ETC sensors sense the position of the accelerator pedal and send electronic signals to the controller. The controller uses the throttle control signal as one basis (among others) for controlling various aspects of the powertrain such as adjusting the air/fuel flow to the engine, shifting of the transmission, etc. In vehicles with ETC systems, the driver indirectly controls the engine and powertrain through the controller.
ETC systems can also coordinate the engine speed with the shifting of the transmission. Direct mechanical systems often shift under high-load conditions, which may decrease the life of the transmission. In ETC systems, the powertrain controller decreases the throttle, shifts, and then increases the throttle. This shifting approach can increase the life of the transmission.
ETC has other benefits as well. Because the driver no longer directly controls the throttle, the powertrain controller can reduce emissions and increase fuel efficiency. Furthermore, the throttle settings can be modified electronically to provide cruise and traction control functions.
Vehicles incorporating ETC systems are designed to prevent malfunctions. To that end, these vehicles usually provide redundancy and perform periodic onboard diagnostic checks. Some vehicles control powertrain torque via one or more algorithms that check powertrain safety critical torque. The algorithms are executed by an engine control module that typically includes a main processor and a motor control processor. For vehicles that do not include a transmission control module, a power control module typically includes the main processor and the motor control processor.
The main and motor control processors redundantly calculate the ETC security algorithms and check the powertrain safety critical torque for validity. In future applications, the ETC algorithms may not be responsible for powertrain torque control. Examples where ETC algorithms are not responsible for powertrain torque control include coordinated torque control, continuously variable transmissions and other powertrain torque modifiers. In these systems, it is essential to develop a powertrain architecture and control algorithms that will validate powertrain torque requests.